Discovered in 1921, BCG is still the only tuberculosis vaccine. But it does not provide protection against severe forms of childhood tuberculosis. There is therefore an urgent need to develop a more effective vaccine against the most prevalent form of the disease: adult pulmonary tuberculosis… Relying on a mouse model, Eva Kaufmann and her coauthors found that when BCG is administered in a way that enables access to bone marrow, it can reprogram the hematopoietic stem cells (HSCs). Once in the marrow, BCG can lead the HSCs to produce monocytes and macrophages, which constitute the first line of defence against the disease.